/*
 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package fr.toto.files;

import static java.nio.file.LinkOption.NOFOLLOW_LINKS;
import static java.nio.file.StandardWatchEventKinds.ENTRY_CREATE;
import static java.nio.file.StandardWatchEventKinds.OVERFLOW;

import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.FileVisitOption;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.WatchEvent;
import java.nio.file.WatchEvent.Kind;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import fr.toto.constantes.Constantes;
import fr.toto.exceptions.ProcessException;

public class WatchDir implements Runnable, Constantes {

	private final WatchService watcher;
	private final Map<WatchKey, Path> keys;
	private final boolean recursive;
	private final ActionFile af;

	@SuppressWarnings("unchecked")
	static <T> WatchEvent<T> cast(WatchEvent<?> event) {
		return (WatchEvent<T>) event;
	}

	private void register(Path dir) throws IOException {
		WatchKey key = dir.register(watcher, ENTRY_CREATE);
		keys.put(key, dir);
	}

	private void registerAll(final Path start) throws IOException {

		Files.walkFileTree(start,EnumSet.noneOf(FileVisitOption.class),
				Integer.MAX_VALUE, new SimpleFileVisitor<Path>() {
			@Override
			public FileVisitResult preVisitDirectory(Path dir,
					BasicFileAttributes attrs) throws IOException {

				register(dir);
				return FileVisitResult.CONTINUE;

			}
		});
	}

	private void initScan(final Path start) throws IOException {
		int maxDepth = 1;
		if (recursive)
			maxDepth = Integer.MAX_VALUE;

		Files.walkFileTree(start, EnumSet.noneOf(FileVisitOption.class),
				maxDepth, new SimpleFileVisitor<Path>() {
					@Override
					public FileVisitResult visitFile(Path file,
							BasicFileAttributes attrs) throws IOException {
						af.executer(file);
						return FileVisitResult.CONTINUE;
					}
				});
	}

	public WatchDir(boolean recursive, ActionFile af) throws IOException {
		this.recursive = recursive;
		this.watcher = FileSystems.getDefault().newWatchService();
		this.keys = new HashMap<WatchKey, Path>();
		this.af = af;
	}

	public void addDir(Path dir) throws IOException {
		if (settings.isDebug())
			System.out.print(String.format(DEBUGMSG.getString("startWatchDir"), dir));
		initScan(dir);
		if (recursive)
			registerAll(dir);
		else
			register(dir);
		if (settings.isDebug())
			System.out.print(DEBUGMSG.getString("processComplete"));
	}

	public WatchDir(Path[] dirs, boolean recursive, ActionFile af)
			throws IOException {
		this(recursive, af);

		for (Path dir : dirs) {
			if (dir.isAbsolute())
				this.addDir(dir);
		}

	}

	public WatchDir(String[] dirs, boolean recursive, ActionFile af)
			throws IOException {
		this(recursive, af);

		if (dirs == null)
			return;

		for (String dir : dirs) {
			if (Files.exists(Paths.get(dir)))
				this.addDir(Paths.get(dir));
		}

	}

	public WatchDir(Path dir, boolean recursive, ActionFile af)
			throws IOException {
		this(recursive, af);
		this.addDir(dir);
	}

	public WatchDir(List<Path> dirs, boolean recursive, ActionFile af)
			throws IOException {
		this(recursive, af);

		if (dirs == null)
			return;

		for (Path dir : dirs) {
			if (Files.exists(dir))
				this.addDir(dir);
		}

	}

	public void run() {
		for (;;) {

			WatchKey key;
			try {
				key = watcher.take();
			} catch (InterruptedException x) {
				return;
			}

			Path dir = keys.get(key);
			if (dir == null) {
				System.err.println("WatchKey not recognized!!");
				continue;
			}

			for (WatchEvent<?> event : key.pollEvents()) {
				Kind<?> kind = event.kind();

				if (kind == OVERFLOW) {
					continue;
				}

				WatchEvent<Path> ev = cast(event);
				Path name = ev.context();
				Path child = dir.resolve(name);

				af.executer(child);

				if (recursive && (kind == ENTRY_CREATE)) {
					try {
						if (Files.isDirectory(child, NOFOLLOW_LINKS)) {
							addDir(child);
						}
					} catch (IOException e) {
						new ProcessException(e);
					}
				}
			}

			boolean valid = key.reset();
			if (!valid) {
				keys.remove(key);

				if (keys.isEmpty()) {
					break;
				}
			}
		}
		
	}
}
